DE102009037285A1 - Exhaust system for internal combustion engine, has exhaust pipe, exhaust gas purification unit, another exhaust gas purification unit, bypass line for turning latter exhaust gas purification unit and exhaust gas return line - Google Patents

Abstract

The invention relates to an exhaust system of an internal combustion engine, which exhaust system comprises an exhaust line, a first exhaust gas purification device, a second exhaust gas purification device, a bypass line for bypassing the second exhaust gas purification device and an exhaust gas recirculation line, wherein a shut-off device is provided in the bypass line with which, depending on an operating point, the Internal combustion engine, the bypass line can be shut off. Furthermore, the exhaust gas recirculation line is connected to the bypass line, with a branch point of the bypass line being positioned between the first exhaust gas cleaning device and the second exhaust gas cleaning device.

Description

The The invention relates to an exhaust system for an internal combustion engine according to the preamble of claim 1.

At the Operation of modern, lean-burned internal combustion engines, such as For example, gasoline engines, in addition to a 3-way catalyst also used NOx storage catalysts. Of the optimum efficiency of such a NOx storage catalyst is usually in a temperature window between approx. 200 ° C and 400 ° C, whereby the storage capacity for NOx emissions deteriorates below or above these temperatures. About that In addition, NOx storage catalysts from a temperature above extremely loaded by 750 ° C, resulting in rapid aging leads.

In order to optimize the operation of a NOx storage catalytic converter during operation, the exhaust gases are diverted, for example, at operating points of the internal combustion engine in which the exhaust gas has high exhaust gas temperatures to the NOx storage catalyst. In the EP 540 280 B1 an exhaust system for an internal combustion engine is described, in which by means of a bypass line, the exhaust gases are diverted to a NOx catalyst arrangement. Furthermore, from the DE 10 2005 017 863 A1 an exhaust gas discharge system for an internal combustion engine is known, in which in a Abgasleitungsstrang a butterfly valve is provided, with which a diversion of the exhaust gases is achieved around a starting catalyst. In this case, the shut-off valve is closed in a starting phase, wherein a Abgasleckagestrom is exhausted in the first exhaust pipe line via a connected to the intake system of the internal combustion engine pressure line.

In addition, in the DE 43 32 086 C2 an exhaust gas purification system for an internal combustion engine is described in which the internal combustion engine is formed from two rows of cylinders, wherein for each cylinder row an exhaust line is provided with an exhaust pipe. Depending on the load point of the internal combustion engine and depending on the catalyst temperature, an inlet opening of the catalyst is closed with the aid of a switching valve in order to divert the exhaust gas via a diversion into the other exhaust pipe. Moreover, in the DE 100 09 541 A1 describes an internal combustion engine, in which premature aging of a NOx storage catalytic converter is prevented by an exhaust gas cooler arranged upstream of the NOx storage catalytic converter.

Of the Invention is therefore the object of an internal combustion engine to provide an exhaust system with a NOx storage catalyst at an improved operation is achieved. This is inventively by the features of claim 1 solved.

The inventive exhaust system is characterized from that the exhaust gas recirculation line with the bypass line is connected, wherein a removal point or a branch point the bypass line between the first exhaust gas purification device and the second exhaust purification device is positioned. Preferably is the first exhaust gas purification device as a 3-way catalyst and the second exhaust gas purification device as a NOx storage catalyst educated. According to the invention, overheating prevents the NOx storage catalyst, depending on the load point the internal combustion engine, an optimized efficiency of the NOx storage catalyst can be adjusted. At the same time, by connecting the Exhaust gas recirculation line on the bypass line Exhaust gas leakage current is sucked off with closed bypass line and the internal combustion engine are supplied. As a result, will with closed bypass line, and in particular in the operating points the internal combustion engine, where high NOx emissions occur, ensured that no NOx emissions without a catalytic Treatment in the environment. Is through the bypass line an exhaust gas recirculation rate higher than one Leakage current is set, such a leakage current of the exhaust gas is almost completely and reliably suppressed. Alternatively, the shut-off device is in the form of an actuatable Flap disposed at the branch point from which the bypass line emanates. Consequently, when opening the bypass line a Blocking the exhaust pipe and vice versa can be achieved.

To An embodiment of the invention is a connection point of Exhaust gas recirculation line with the bypass line downstream the shut-off device positioned. As a result, when the bypass line is closed ensures that there are no NOx emissions through the bypass line get into the environment. Alternatively, the junction of the Exhaust gas recirculation line with the bypass line upstream the shut-off device positioned. As a result, a leakage mass flow withdrawn from the bypass line within the bypass line and the internal combustion engine supplied again. In particular the lean-burned internal combustion engines, such as gasoline engines, for Minimization of raw NOx emissions anyway operated with high exhaust gas recirculation rates be leads, such an arrangement in which the exhaust gas recirculation line connected to the bypass line, no significant additional effort. To the driving gradient over the shut-off device to hold high, is alternatively the connection point of the exhaust gas recirculation line positioned with the bypass line within the shut-off device.

According to another aspect of the invention the exhaust system includes a first exhaust line and a second exhaust line, wherein the first exhaust line of a first cylinder group of the internal combustion engine and the second exhaust line is associated with a second cylinder group of the internal combustion engine. According to the invention, a first exhaust gas purification device, a second exhaust gas purification device for bypassing the second exhaust gas purification device, a first bypass line and an exhaust gas recirculation line is arranged in each exhaust line, wherein in the first bypass line a shut-off device is provided, with which the bypass line in dependence on an operating point of the internal combustion engine can be shut off , Furthermore, an exhaust gas adjustment device is arranged in the exhaust gas recirculation line, wherein the exhaust gas recirculation line is connected to the first bypass line. Preferably, a removal point or a branch point of the first bypass line is positioned between the first exhaust gas purification device and the second exhaust gas purification device. As a result, the exhaust system according to the invention is also suitable for internal combustion engines with two rows of cylinder banks. Preferably, the first exhaust gas purification device is designed as a 3-way catalytic converter and the second exhaust gas purification device as a NOx storage catalytic converter.

To an advantageous embodiment of the invention, both of first exhaust line and the second exhaust line each a second Bypass line on, the removal point or branch point between the first exhaust gas purification device and the second exhaust gas purification device is positioned. Preferably, the exhaust gas flow of the first exhaust line in the second exhaust line via the second bypass line the first exhaust line. This can be a Bypassing of the second exhaust gas purification device in the first exhaust gas line be achieved.

According to one Another embodiment of the invention, the exhaust gas flow of the second Exhaust line in the first exhaust gas line through the second exhaust pipe the second exhaust line. This can also be done a bypass of the second exhaust gas purification device in the second Exhaust line can be effected. This results in improved operation the exhaust system, so that the NOx storage catalyst in an optimized Efficiency can be operated.

Further Features and combinations of features result from the description. Concrete embodiments of the invention are shown in the drawings shown simplified and in the following description in more detail explained. Showing:

1 a schematic representation of an exhaust system according to the invention according to a first embodiment,

2 a schematic representation of the exhaust system according to the invention according to a second embodiment,

3 a schematic representation of the exhaust system according to the invention according to a third embodiment and

4 a schematic representation of a modified embodiment of the exhaust system according to 3 ,

In 1 is an exhaust system 1 an internal combustion engine 2 shown in simplified, the exhaust system 1 an exhaust pipe 3 , a first exhaust gas purification device 5 and a second exhaust purification device 6 includes. A bypass line 4 is to bypass the second exhaust gas purification device 6 intended. According to the invention is also an exhaust gas recirculation line 9 at the bypass line 4 connected, from the exhaust gas into the intake manifold 12 the internal combustion engine 2 is returned. In addition, at the exhaust gas recirculation line 9 an exhaust gas adjustment device 7 provided, with which the recirculated exhaust gas quantity is controlled. Preferably, the first exhaust gas purification device is designed as a 3-way catalytic converter, wherein the second exhaust gas purification device 6 is designed as a NOx storage catalyst. According to the invention is between the 3-way catalyst 5 and the NOx storage catalyst 6 a sampling point or branch point 11 positioned by the bypass line 4 emanates.

The exhaust gas of the internal combustion engine 2 passes from an exhaust manifold, not shown in the exhaust pipe 3 , then close to the engine 2 positioned 3-way catalyst 5 and then to the NOx storage catalyst 6 , To the second exhaust gas purification device or the NOx storage catalyst 6 at certain operating points of the internal combustion engine 2 To protect against high exhaust gas temperatures, the bypass line 4 by a shut-off device positioned therein 8th for diverting the exhaust gas into the bypass line 4 open. The exhaust gas then flows through the bypass line 4 because there is a low flow resistance here. Alternatively, the shut-off device 8th in the form of an operable flap at the branching point 11 arranged so that when opening the bypass line 4 a blockage of the exhaust pipe 3 and vice versa can be achieved.

Usually forms with closed bypass line 4 an exhaust gas leakage stream at the shut-off device 8th caused by the connection of the exhaust gas recirculation line 9 with the bypass line 4 abge sucks and the suction pipe 12 the internal combustion engine 2 can be supplied. Accordingly, when the bypass line is closed 4 , And in particular in the operating points of the internal combustion engine, where high NOx emissions incurred, ensures that when the shut-off device is closed 8th No NOx emissions through the bypass line 4 get outside.

According to a first embodiment, the exhaust gas recirculation line 9 according to 1 downstream of the shut-off device 8th with the bypass line 4 connected. This is at the bypass line 9 a junction 9a downstream of the shut-off device 8th provided, from which the exhaust gas via the exhaust gas recirculation line 9 in the suction pipe 12 the internal combustion engine is returned.

According to a second embodiment of the invention is according to 2 the connection point 9a the exhaust gas recirculation line 9 upstream of the shut-off device 8th positioned. Accordingly, in the intake manifold 12 the internal combustion engine 2 recirculated exhaust gases before the shut-off device 8th aspirated. By connecting the exhaust gas recirculation line 9 with the bypass line 4 upstream of the shut-off device 8th it is ensured that an exhaust gas leakage flow is extracted. Consequently, when the shut-off device is closed 8th enter from non-catalytic exhaust gas into the open via the bypass line 4 prevented.

According to a third embodiment is according to 3 an internal combustion engine 20 shown with two rows of cylinder banks. Here is the exhaust system according to the invention with a further bypass line 24 respectively. 25 Mistake. Accordingly, the exhaust system includes 1 a first exhaust line 26 and a second exhaust line 27 , The first exhaust system 26 is assigned to a first cylinder group, wherein the second exhaust line of a second cylinder group of the internal combustion engine 20 assigned.

Each exhaust system consists of an exhaust pipe 13 in the near of the internal combustion engine 2 positioned portion of a first exhaust gas purification device 15 is positioned. A second exhaust gas purification device 16 is always in each exhaust system 26 and 27 positioned. Furthermore, a first bypass line 14 for bypassing the second exhaust gas purification device 16 intended. Furthermore, each exhaust system comprises 26 respectively. 27 a first silencer 21 and a second muffler 22 , Preferably, the first muffler 21 in the first bypass line 14 positioned.

Furthermore, each exhaust system comprises 26 respectively. 27 an exhaust gas recirculation line 19 that with the first bypass line 14 connected is. in the first bypass line 14 is a shut-off device 18 provided with the bypass line 14 as a function of an operating point of the internal combustion engine 20 can be locked. The junction of the exhaust gas recirculation line 19 with the first bypass line 14 can be downstream, upstream or inside the shut-off device 18 the bypass line 14 respectively.

In addition, in the exhaust gas recirculation line 19 an exhaust gas adjustment device 17 positioned. Preferably, a removal point or a branch point 11 the first bypass line 14 between the first exhaust gas purification device 15 and the second exhaust purification device 16 positioned. Consequently, the exhaust system according to the invention is also suitable for internal combustion engines with two rows of cylinder banks. In particular, the first exhaust gas purification device 15 as a 3-way catalyst and the second exhaust gas purifier 16 formed as a NOx storage catalyst.

According to the third embodiment is in each exhaust system 26 and 27 another branch point 29 downstream of the 3-way catalyst 15 provided by a second bypass line 24 respectively. 25 goes out and extends into the other exhaust system. Accordingly, goes from the branch point 29 of the first exhaust line 26 downstream of the 3-way catalyst 15 the second bypass line 24 out, extending into the second exhaust system 27 extends. The second bypass line 24 respectively. 25 flows into the exhaust pipe 13 upstream or alternatively downstream of the sampling point 11 the first bypass line 14 ,

At the junction 29 is in every exhaust system 26 respectively. 27 an exhaust flap 28 arranged. Depending on the position of this exhaust flap 28 the exhaust gas flow of the respective exhaust system is in the other exhaust line 26 respectively. 27 diverted. For example, by closing the exhaust pipe 13 with the exhaust flap 28 of the first exhaust line 26 the complete exhaust gas flow of the first exhaust gas line 26 in the first bypass line 24 and thus in the exhaust system 27 diverted.

Here are the dimensions of the bypass lines 24 and 25 chosen such that, for example, the exhaust gas flow of the first exhaust line 26 if this in the second bypass line 24 is diverted a longer distance to reach the NOx storage catalyst 16 of the second exhaust line 27 than until reaching the NOx storage catalyst 16 of the first exhaust line 26 , This allows the exhaust gas of the first exhaust line 26 until entry into the NOx storage catalytic converter 16 of the second exhaust line 27 cool down more. To reinforce this effect is optionally an unillustrated exhaust gas cooler arranged in front of the respective NOx storage catalyst, with which the exhaust gases can be further cooled before entering the respective NOx storage catalyst.

Depending on the operating point of the internal combustion engine, the exhaust pipe 13 with the help of an optional shut-off valve 30 closed, immediately before the NOx storage catalyst 16 is positioned to the exhaust via the first bypass line 14 redirect. According to a modified embodiment of the third embodiment, the exhaust gas recirculation line 19 according to 4 both for the first exhaust system 26 as well as for the second exhaust system 27 summarized. Accordingly, the exhaust gas recirculation line 19 through an exhaust connection pipe 19a with the first bypass line 14 of the first exhaust line 26 connected, with another connecting line 19b the exhaust gas recirculation line 19 with the first bypass line 14 of the second exhaust line 27 combines. To cool the recirculated exhaust gases is in the exhaust gas recirculation line 19 an exhaust gas cooler 23 positioned.

In operation of the internal combustion engine 2 respectively. 20 becomes the 3-way catalyst 5 and 15 warmed up quickly so that they reach an optimal operating temperature. To the NOx storage catalyst 6 respectively. 16 At certain operating points of the internal combustion engine to protect against high exhaust gas temperatures, according to the invention, the first bypass line 14 and / or the second bypass line 24 respectively. 25 to be activated. To divert the exhaust gas into the corresponding bypass line, the respective exhaust valves 28 , the shut-off devices 18 and / or the shut-off valves 30 Operating point dependent actuated. For the purposes of the invention, both the first and the second bypass lines 14 . 24 respectively. 25 partially or completely activated or deactivated. D. h., The exhaust gas flow can be divided depending on the load point of the internal combustion engine to the different bypass lines to ensure the best possible operation and optimum protection of the respective NOx storage catalyst. Accordingly, a combined activation of the first and the second bypass lines in the context of the invention can take place. By the arrangement of the first 14 or the second bypass lines 24 and 25 it is ensured that the NOx storage catalytic converters are not damaged by the warming up of the exhaust gases in the respective 3-way catalytic converter.

A cooling of the through the bypass lines 24 and 25 diverted exhaust gases is achieved by the extended exhaust pipe in this way, wherein during a cold start phase of the internal combustion engine 20 a diversion of the exhaust gas via the bypass lines 24 and 25 is not made, allowing rapid heating of the NOx storage catalysts 16 achieved by the shorter route. As a result, an optimum operating temperature of the NOx storage catalysts is set rapidly during a cold start phase.

For the purposes of the invention, depending on the nature of the exhaust gas composition, further catalysts of any kind may be present within the exhaust system 1 be included. Although the present invention is particularly well suited for lean-burn gasoline engines, the exhaust gas system according to the invention 1 be used for any type of internal combustion engine. In particular, the exhaust system according to the invention 1 also in diesel engines, even using particulate filters or similar catalysts are used.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 540280 B1 [0003]
• DE 102005017863 A1 [0003]
• - DE 4332086 C2 [0004]
• - DE 10009541 A1 [0004]

Claims (15)

Exhaust system ( 1 ) an internal combustion engine ( 2 . 20 ), with an exhaust pipe ( 3 . 13 ), a first exhaust gas purification device ( 5 . 15 ), a second exhaust gas purification device ( 6 . 16 ), a bypass line ( 4 . 14 . 24 . 25 ) for bypassing the second exhaust gas purification device ( 6 . 16 ), and an exhaust gas recirculation line ( 9 . 19 ), whereby in the bypass line ( 4 . 14 ) a shut-off device ( 8th . 18 ) is provided, with the function of an operating point of the internal combustion engine ( 2 . 20 ) the bypass line ( 4 . 14 ) is shut off, and wherein in the exhaust gas recirculation line ( 9 . 19 ) an exhaust gas adjustment device ( 7 . 17 ), characterized in that the exhaust gas recirculation line ( 9 . 19 ) with the bypass line ( 4 . 14 ) and wherein a branch point ( 11 . 29 ) of the bypass line ( 4 . 14 . 24 . 25 ) between the first exhaust gas purification device ( 5 ) and the second exhaust gas purification device ( 6 ) is positioned. Exhaust system ( 1 ) according to claim 1, characterized in that a connection point ( 9a ) of the exhaust gas recirculation line ( 9 . 19 ) with the bypass line ( 4 . 14 ) downstream of the shut-off device ( 8th . 18 ) is positioned. Exhaust system ( 1 ) according to claim 1, characterized in that the connection point ( 9a ) of the exhaust gas recirculation line ( 9 . 19 ) with the bypass line ( 4 . 14 ) upstream of the shut-off device ( 8th . 18 ) is positioned. Exhaust system ( 1 ) according to claim 1, characterized in that the connection point ( 9a ) of the exhaust gas recirculation line ( 9 . 19 ) with the bypass line ( 4 . 14 ) within the shut-off device ( 8th . 18 ) is positioned. Exhaust system ( 1 ) according to one of claims 1 to 4, characterized in that the exhaust system ( 1 ) a first exhaust line ( 26 ) and a second exhaust line ( 27 ), wherein the respective exhaust gas line is associated with a first cylinder group of the internal combustion engine or a second cylinder group of the internal combustion engine. Exhaust system ( 1 ) according to claim 5, characterized in that both the first exhaust gas line ( 26 ) as well as the second exhaust gas line ( 27 ) each have a first bypass line ( 4 . 14 ) whose branching point ( 11 . 29 ) between the first exhaust gas purification device ( 5 . 15 ) and the second exhaust gas purification device ( 6 . 16 ) is positioned. Exhaust system ( 1 ) according to claim 5 or 6, characterized in that both the first exhaust gas line ( 26 ) as well as the second exhaust gas line ( 27 ) each have a second bypass line ( 24 . 25 ) whose branching point ( 29 ) between the first exhaust gas purification device ( 5 . 15 ) and the second exhaust gas purification device ( 6 . 16 ) is positioned. Exhaust system ( 1 ) according to any one of claims 5 to 7, characterized in that for bypassing the second exhaust gas purification device ( 6 . 16 ) in the first exhaust gas line ( 26 ) the exhaust gas flow of the first exhaust gas line ( 26 ) in the second exhaust line ( 27 ) through the second bypass line ( 24 ) of the first exhaust line ( 26 ) is transferred. Exhaust system ( 1 ) according to one of claims 5 to 8, characterized in that in order to bypass the second exhaust gas purification device ( 6 . 16 ) in the second exhaust line ( 27 ) the exhaust gas flow of the second exhaust gas line ( 27 ) in the first exhaust line ( 26 ) through the second bypass line ( 25 ) of the second exhaust line ( 27 ) is transferred. Exhaust system ( 1 ) according to one of claims 1 to 9, characterized in that the first exhaust gas purification device ( 5 ) is a three-way catalyst. Exhaust system ( 1 ) according to one of claims 1 to 10, characterized in that the second exhaust gas purification device ( 6 ) is a NOx storage catalyst. Exhaust system ( 1 ) according to one of claims 1 to 11, characterized in that on the exhaust gas recirculation line ( 9 . 19 ) A cooling device is provided. Exhaust system ( 1 ) according to one of claims 1 to 12, characterized in that both the first exhaust gas line ( 26 ) as well as the second exhaust gas line ( 27 ) one each the exhaust gas recirculation line ( 19a . 19b ), which with the respective bypass line ( 4 . 14 ) connected is. Exhaust system ( 1 ) according to one of claims 1 to 13, characterized in that the exhaust gas recirculation line ( 19a ) of the first exhaust line ( 26 ) and the exhaust gas recirculation line ( 19b ) of the second exhaust line ( 27 ) in a common exhaust gas recirculation line ( 19 ). Exhaust system ( 1 ) according to one of claims 1 to 14, characterized in that a shut-off valve ( 30 ) between the second exhaust gas purification device ( 6 . 16 ) and the branch point ( 11 ) of the first bypass line ( 4 . 14 ) is positioned.

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